def d(n,n0):
    """d returns the discrete impulse function evaluated for the values in n (numpy array) with an offset n0.
    Inputs :
     * n :   numpy.array of int, discrete values where the discrete impulse function will be evaluated
     * n0 :  int, offset of the discrete impulse function

    Outputs :
     * y :   numpy.array, discrete values of the discrete impulse signal evaluated for the input n

    Creation  : 14-02-2020
    """

    index_arr = np.where(n==n0)
    n = np.zeros(len(n))
    for index in index_arr:
        n[index] = 1
    return n

def u(n,n0):
    """u returns the step function evaluated for the values in n (numpy array) with an offset n0.
    Following the mathematic definitions:
        - u(n,n0) = 1 for every i in n such that i>=n0
        - u(n,n0) = 0 for every i in n such that i<n0
    Inputs :
     * n :   numpy.array of int, discrete values where the step function will be evaluated
     * n0 :  int, offset of the step function

    Outputs :
     * y :   numpy.array, step function evaluated for n with offset n0

    Creation  : 14-02-2020
    """
    out = np.empty(len(n))
    for i in range(0,len(n)):
        if (n[i]<n0):
            out[i] = 0
        else:
            out[i] = 1
    return out

def r(n,n0):
    """r returns the ramp function for the discrete values in n with offset n0
    Inputs :
     * n :   numpy.array of int, discrete values where the ramp function will be evaluated
     * n0 :  int, offset of the ramp function

    Outputs :
     * y :   numpy.array, ramp function evaluated for n with offset n0

    Creation  : 14-02-2020
    """
    out = np.empty(len(n))
    for i in range(0,len(n)):
        if(n[i]-n0<=0):
            out[i] = 0
        else:
            out[i] = n[i]-n0
    return out

def plotFig(y,n,name):
    """plotFig stem plot n for x axis and y for y axis and save the plot as an png
    Inputs :
     * y :    array_like, the y axis values to be plotted
     * n :    array_like, the x axis values to be plotted
     * name : string, name given to the saved png file

    Creation  : 14-02-2020
    """
    # Création de la figure, de taille fixe.
    plt.figure(figsize=(6,3))

    (markerLines, stemLines, baseLines) = plt.stem(n,y,label="Signal")

    plt.setp(markerLines,color="white",markeredgecolor = 'black')
    plt.xlabel("n (seconds)")
    plt.ylabel("y[n]")
    plt.title("Signal plot {}".format(name))

    # Sauvegarde de la figure avec le bon noms.
    # Le second argument rétrécit les marges, par défaut relativement larges.
    plt.savefig(name + '.png', bbox_inches='tight')